21 



on the amcebse in thirty minutes and 1-250 a decided one in 

 twenty minutes. 



Nitrate of silver, thymol, benzoyl acetyl peroxide, and acid suc- 

 cinic peroxide in moderate strength exercised a marked effect on the 

 amoebae, whereas sulphate of copper, permanganate of potassium, 

 tannic acid, infusion of quassia, ichthyol, and oil of cassia had but a 

 slight one. 



In order to determine more accurately the effect of these and 

 other substances on the unprotected amoeba, another series of tests 

 was undertaken on the amtcbse suspended in fluid, and in order 

 to determine whether the deleterious action of each substance was 

 due to a specific action on the amoebae or to the destruction or 

 attenuation of its symbiotic bacteria, synchronous transplants were 

 made from the treated culture to sterile agar plates and to others 

 previously inoculated with the cholera spirillum. 



Uniform suspensions of the amoebae were made by pouring 

 4 cubic centimeters of distilled, sterile water over the surface of a 

 forty-eight -hour slant agar culture of the amoeba and cholera spiril- 

 lum, scraping off the surface growth, mixing with the water by 

 means of a platinum wire, and pouring the resultant suspension into 

 a sterile test tube. Four cubic centimeters (in double strength) of 

 the antiseptic solution to be tested were then added to the 4 cubic 

 centimeters of suspension of amoebae, thus making a fairly uniform 

 solution of 8 cubic centimeters of liquid to one forty-eight-hour 

 slant culture, the mixture containing a definite amount of the 

 cliemical to be tested. The suspension was next thoroughly shaken 

 and allowed to stand for the desired lengths of time, and then 

 transfers of one loop of the suspension were made to Petri dishes 

 containing the special agar medium, and allowed to develop for 

 forty-eight hours. At the end of such time the plates were care- 

 fully examined for amoebae and bacteria. As stated before, similar 

 transplants were made at the same time to plates previously inocu- 

 lated with the cholera spirillum. To minimize the concentration 

 of the small quantity of antiseptic carried over with the loop of 

 suspension, the droplet was spread over a circular area about one- 

 half inch in diameter in the center of the agar plates. 



The following taljlo epitomizes the results of such experiments 

 as were carried out with a maximum degree of uniformity and 

 accuracy. Many more tests besides those tabulated were made with 

 eacli substance, substantiating in the main the results set forth in 



